No two ways about it. Worrying about your health can make you sick. It's bad enough when you're ill, but it's a blinder if there's nothing wrong with you. Though we live longer and are healthier than before, the richer and healthier you get, paradoxically the more likely you are to feel you are to be unhappy about your health and seek treatment. Self-reported illness in the Indian state of Bihar, which has the lowest life expectancy in India, is a fraction of that in the US.

Part of the problem in developed countries is that things we never thought of as medical complaints are now presented as diseases which must be prevented and treated. Ageing, for example, or shyness. A coincidence that there are now said to be pills for each of these ills? Actually, it's hormone top-ups if you are a man of 70 wanting to follow through after downing an anti-shyness elixir.

Some of these new diseases - female sexual dysfunction comes to mind - do exist and should be treated, but I'll lay you a dollar to a doughnut that claims by the drug companies peddling treatments for this condition, that 40% of women are afflicted by it, are wide of the mark. Does one episode of fumbled dissatisfaction constitute sexual dysfunction? No, but once a doubt slips into the mind, it can find fertile ground. Remember how Blake's poison tree grew:

And I watered it in fears, Night and morning with my tears; And I sunned it with smiles, And with soft deceitful wiles.

One of the wiles most often practised by drug companies is that of making healthy people feel unhealthy. Risk is heavily emphasised. For instance, in the national press, against a picture of smiling happy healthy people, Johnson & Johnson advertises Zocor, a cholesterol lowering drug now available through pharmacists, with the line "my risk [of a heart attack] could be as much as one in seven", where the risk refers to the risk of heart attack in the next 10 years. When the ad first appeared, Which? magazine complained to the Advertising Standards Authority on the grounds that it exaggerated a risk, which could be as low as one in 10. Their objection was not upheld.

The ASA took the view that if you had a tick in every box on the risk scorecard, then the risk would be as stated, and was thus factually correct. File under S for soft wile would be my opinion.

There is rather more money to be made from selling drugs to the healthy than there is in peddling them to the sick. The numbers are clear. The majority of people are healthy, while a minority are sick. Furthermore those that are sick can't work and are unlikely to have the money to pay for drugs that enhance wellness, rather than cure sickness. You don't have to be Alan Sugar's apprentice to spot the opportunity.

But there are many dangers in medicalising wellness. Risk factors such as high blood pressure, thinning bones and even age are treated as if they were disease states in themselves, rather than part of a spectrum. Being labelled "at risk" has a largely un known impact, but it would not surprise if, having "watered it in fears," symptoms became apparent.

The healthy are complicit in the medicalising of wellness, particularly those in middle life, for it promises to turn back time, to redeem us from poor lifestyles and indulgence, with a one-a-day wonder worker. Changing our lifestyle would more appropriate but much harder. And when we are all committed to pills to sort out our lifestyle problems, we may breathe a sigh of relief, but somewhere, among the hordes required to show benefit in preventive medicine, are certainly those made ill by the very medicines designed to keep the rest of us well.

Preventive medicine at its best is a modern miracle. Large-scale population interventions have saved millions of lives at relatively small cost. The immunisation programmes that have eliminated smallpox from the world; improved sanitation that has driven back malaria and made cholera less common; workplace improvements that have eliminated occupational cancers.

Iona Heath, a GP writing in the British Medical Journal, has called for a tax on preventive medicines to be used to buy medicines for those with treatable disease in poorer nations. We could do this. But we could also stop spending vast sums on preventive drugs, and put that money into population interventions - better quality meals allied to more sport in school, for instance, or banning smoking in public places. Hell, it might even make us happier in the process, and curiously if you really want to prevent ill health, being happy is one of the best prophylactics around. Enjoy being well.